CatSpot Cat Litter is the most lightweight cat litter on the market and is made 100% from the husk of a coconut. Simply comparing weights is not an accurate way to analyze how much product you are getting because the density of the product is different than anything else out there.
There are approximately 18.34 L or 0.65 cubic ft. in a 5 lb. bag of CatSpot Litter. By comparison, if you filled the CatSpot bag with clay litter, it would weigh approximately 20 lbs. and typically, that 20 lbs. of clay only gets you through a portion of one month. You end up having to buy more before that month is up.
As a good rule of thumb, one bag of CatSpot Litter is a one-month supply for one cat.